Partly #3 is the camera angle but otherwise she's just a type I've seen before. A friend of mine built sets for a local theater troop, there was a dancer who seemed to defy the laws of thermodynamics. There was just no way the internal organs which could be fitted in to her relatively tiny body cavity could power her comparatively huge legs and arms.

If there were there would be tell tale signs in the warping or reproduction of shapes/patterns in the background image. There are none. Also there are faint undulations where you can see her ribs on the outer edges of her torso. Most attempts at photoshoping would have these straitened and flattened so it would look totally inorganic. This isn't the case.

Photoshop shenanigans are easy to spot when you know what to look for.